Justification:
This species is considered to be Vulnerable due to a small population size and ongoing decline (criterion C) estimated from hunting and inferred from reduction of habitat quality, and following a quantitative analysis (criterion E). The total census population estimation for the species is 12,000-17,000 individuals, of which less than 10,000 are estimated to be mature. The remaining 10,000 mature individuals are divided into subpopulations, each with less than 1,000 mature individuals. Habitat fragmentation is also a serious threat to the existing populations. Additionally, there is a continuing decline in a large portion of the existing range (Argentine and Bolivia), where the cumulative population between both these countries may not reach 2,000 mature individuals. A PVA on a healthy population in southern Peru showed a high probability of extinction (<10% in 100 years), further justifying a Vulnerable listing. The scenario from Peru is representative of the whole population. Also, vicuña (Vicugna vicugna) Peruvian census data from 1988 included taruka in some areas, and following local people accounts in those areas, the taruka population had decreased more than 50% in the previous 20 years (1960s to 1980s). A similar trend was obtained in recent years by Javier Barrio in three separated areas from Peru.

The taruka occurs as scattered populations with very little contact areas among them, a distribution explained by the specialized habitat it uses. Its distribution can be regarded as almost continuous along the highlands of the Andes from the north of Peru to northeastern Chile, but we should be aware that the habitat type used is isolated in some areas, and human density is high between patches. The taruka occurs in heavily fragmented populations throughout the high Andes of Bolivia—with no records in the southwest—, and in northwest Argentina. The historical distribution was probably the same as the actual one, but populations might have been less fragmented then. Contrary to several publications (Geist 1998; Weber and Gonzalez 2003; Wemmer 1998), the taruka has never occurred in Ecuador. It is unlikely that the taruka has ever crossed north of the Huancabamba depression in north Peru, even during the Pleistocene, when the habitat type it currently uses was lower than present altitude. Then, the high Andes were populated by other deer genera (Hoffstetter 1986; Wheeler et al. 1976). The asseveration of the former presence of taruka in Ecuador was based on doubtful records (Tirira 2001). One specimen in the Buenos Aires museum and another in the Field Museum, Chicago, were marked as coming from Ecuador (Voss 2003), but both have disappeared and could have come from anywhere else, for example Peru or Chile, if they were correctly identified. Another two specimens were deposited in the Museo Nacional de Ciencias Naturales in Madrid (Voss 2003). These were authentic records from Ecuador, as the collector, the collection site and the year were identified (Voss 2003), but both specimens were also lost and there is no way to verify the species.

Based on known densities and censuses for Argentina, Chile and Peru, and estimations for Bolivia, the total population is estimated to be around 12,000–17,000 individuals. Taruka population in Chile might be around 1,000 individuals, based on census data from Sielfeld et al. (1988). Based on calculated densities including all potential areas and on extent of distributional range, total taruka population in Peru may be around 9,000-13,000 individuals, of which—based on known age structure—at least 75% are mature individuals (7-10,000 individuals).

Tarukas have been found at 2,000-3,500 above sea level in the southern portion of their distribution in Argentina (Cajal 1983), at 2,500-4,000 m in northern Chile (Sielfeld et al. 1988), and at 3,500-5,000 m in the highlands of Peru and Bolivia (Barrio 1998, 2004; Jungius 1974; Merkt 1985; Yensen et al. 1994). Tarukas live in areas with wet weather on the eastern Andes (Barrio 2004; Jungius 1974) as well as areas with dry weather on the western Andes (Barrio 1998; Merkt 1985; Sielfeld et al. 1988). Tarukas are usually found above the treeline on mountain slopes characterized by rock and cliff-like outcrops amid grassland vegetation (Barrio 2004; Jungius 1974; Merkt 1985, 1987). Tarukas seem to prefer rocky areas of sparse vegetation with nearby water sources—usually a small ravine, lagoon or marsh (Barrio 2004; Merkt 1985), however, they have been observed in dense shrubbery near rivers and inside Polylepis sp. forests (Barrio, in prep). In several sections of the distribution, taruka populations live in fragmented portions of the range (Barrio 1999; Cajal 1983). The taruka shares its habitat with domestic stock, which might compete with taruka and decrease the area available to them (Barrio 1999, 2004).

The species is included on CITES Appendix I and occurs in several protected areas across its range. Recommended conservation actions include: systematic surveys to determine status and extent of geographic distribution; support continued ecological studies of the species throughout its range; strengthen protected areas management; exclude domestic stock from protected areas with physical barriers and law enforcement; reduce numbers of livestock; improve livestock management through farmer education demonstration projects.

Voss, R. S. 2003. A New Species of Thomasomys (Rodentia: Muridae) from Eastern Ecuador, with Remarks on Mammalian Diversity and Biogeography in the Cordillera Oriental. American Museum Novitates 3421: 1-48.